Driving center



Oct-I E. A. TERRELL DRIVING CENTER Filed Feb. 19, 1941 3 Sheets-Sheet 1 1 S 3. r /W\ MN. m$i

INVENTOR EDGAR A. TERRELL Oct. 26, 1943. I A, TERRELL 2,333,055

DRIVING CENTER Filed Feb. 19, 1941 5 Sheets-Sheet 2 1 1636 37 as as INVENTOR- EDGAR A. TERRELL' TTORNEY 1943- E; A. TERRELL DRIVING CENTER Filed Feb. 19, 1941 3 Sheets-Sheet 3 2 3 & ma 9 g V MR \g m l/ m M i E L 4 4 mm xv mm 3 .2 mm Q Q Q v7 5a v A U A in M4 Z, P

attorney ducing greatly any tendency of the work to slip sidewise or at right angles to its axis as the'driving dogs are forced intov the driven end. This latter resultis obtained, as above suggested, by setting the circular knife edge slightly in ad- Vance of the driving dog knife edges so that the 'Work'is supported against motion away from the true axis of the machine by both the conical point center and-by the knife ring which also engages H it pri'or to engagement with the driving knife edges. 1 V 1 'In' the operation-of my driving center on pre bored work even where the prebored hole assumes anelliptical shape, concentricity of the turned surface with the center hole isobtained; This is accomplished by providing suflicie'nt pressure of the conical center pin engaging the hole to expand the flat sidesof the hole enough to permit its entire circumference to be engaged by the cone, before the knife edge of the sleeve engages the work to give further support against sidewise motion. Thenboth the conical center andthe circular knife will "give combined support to prevent the final force applied to push inthe driving dogs from causing displacement'from" the axis. The circular knife assists further in resisting side stress imposed by the cutting tools and in addition prevents the ring of material 'engaged-by-thedriving dogs from spreading- The material is therefore made stronger and-"denser in that area which is en-- gagd by the driving'dogs.- i

This is 'made possible by the knifeedge of the sleeve being'beveled inwardly so 'that it compresses the material which is brought into contact with the face of the sleeve. The knife ring effectively prevents spreading of the end fibers lyingbetween it and the conical center or center' point. Since the material engaged by the driving dogs is thus strengthened it followsthat greater driving force'can be secured from drivin'g-dogs of a given size than would be the-case if the end fibers were notsupported and com.-

pressed by the outer knife ring. I j I, I I

' It will also be understood that' iffy-positivelyengaged driving dogs; and circular knife'when used, provide substantially greater driving force than can be obtained from a screw type center where'the driving power is transmitted solely by engagement of the screw with the-material. This is true regardless 'ofwhether the screw is adjustable or mounted in'fi'xed position." Mores formed by the sides of the keyways which contain the driving dogs.

,The above describedfdoub-le coneconstruction of the center 'pin is desirable although'notessential to the operation of my device and is used assembly is relative. circumstance the driving center assembly may by using a spring pressed conical center point I slidably mounted to permit slight endwise movement to compensate for slight variations in hole diametenwhile the centering of solid work may require a center point fixedly held against axial movement. My driving center provides for both uses as will be understood from the description to follow. x

It will .be understood that endwise motion between the work piece and the driving center Accordingly under some be moved endwise into complete engagement ariseif it were desirable to move both the driv primarily to gain'the aforementioned advantages v and to save material through shorteningthe total T. Ashereto'fore mentioned-'my center may "be? used onwork which has a prebored hole on length of the cone.

which the work is to be centered or on solid work into which a center pin .must be forced. .The

centering of prebored'workis best accomplished with a stationary work piece while under other circumstances the work piece may be moved 'endwise into engagement with a non-moving driving center assembly. A third condition would Fig. lis a longitudinal sectional view of my fragment of a prebored driving center; anda work piece;

Fig. 2 isan end. View of the driving center shown in' Fig. 1;

Fig; 3 is anelevational' view of the driving dogs and supporting member therefor;

Fig. 4 is an end view of the assembly shown in Fig. 3; 1

Fig.5 is a detail of one of the driving dogs; Figs. 5A and 5B are sectional views along the lines A-A and BB respectively ofthe driving dog shown in Fig. 5; and Figs. 5C and 5D are end views of this driving dog;

Fig. 6 is an elevational view of the sleeve with keyways; V

Fig. '7 is an end Fig. 6;

Fig. 8 is a fragmentary longitudinal sectional view of the driving center having a reduced di ameter double cone, and a prebored work piece.

Fig. 9 is an end View of. the driving center shown in Fig. 8; A

- Fig. 10 is a fragmentaryilongitudinal sectional view, of the driving center having a reduced diameter sleeve, and a prebored work piece.

'- Fig. 11 is an endview of the driving center shown in Fig. 10'; s

Fig. 12 is a longitudinal sectional view of a modification of the driving center shown in Fig. 1;

-Fig. 13 is an end view Fig. 12-; 1 V

- Fig. 14 is a longitudinal sectional view of the of the driving center of driving center using a point type center pin in a tify-similarpartsthe driving center assembly as illustrated in Figs. land 2' comprises a cupshaped body portion l0 having a tubular shank ll which is adapted for attachment to the spin- View of the sleeve shown in I save a r inner end of-the seeveseamg onfth to support it against axial displacement from cutting stresses as described generally above."

*flnside or the sleeve n is'sildably positioned a point" 23 projecting into a longitudinal slot 2! of any particular work piece on which thereon;

in ailatho or other- 'suitable driving} means? m g onflie of miss disk: aha 1 base membr t2"oi suitable 'diameter' to' it snugly within "the inner cireumstance ot the olthe drivingdogsn. i The disk I2 has tappedholesM spaced around the hee s! the-disk equidistant from-the center,

for 'i'eeetving 'the cnreaaeaends s oi the- 'driv lnig dogs' l t, 'lhis threaded connectionprevents rolotlve-endwlse' i'no'tion betweenthe disl and the dogs f during; operation, although ei'ieea cit-shortening of the dogs can be'obtolned when i desired 'by 'rotary motion of the thafi i'sg advancing-or retarding-"the am ao senas nwerost or metappea holes or sleeve {l6} tlfie general iatureso which are redene'd 'to'hereinabove, locatedinsi the {fl-and" in relatively close coi'itactftherewith. Itr'ests on the disk or base antelu and is; held 1h 'yflxjed position by i a Set scre ti eless-prevents m aifial androtary motion of'the'sleevei 1 The several purposesyof'lwhieh the fellobwing are principal earamples; I 4

diskfl prevents the latter Irom movingjendwise myn'mmebottom of'the cup.

sleeve is slotted axially along the inner surface to form keyways for receiving and holdingthe driving; dogs ll. The-keyways find-dogs sided or -of such cross-section that'fthe dogs cannot rotate'wh'en located in the keyways'l Thus when the sleeve is assembled with eup H disk lhdrivingdogs l3" and setscrew l1, the

ammblr'ls 0 together as-a a "ms side walls -ll'of theslots orfllreyways sup port the 'drlvingdegs Ii -against torsion imparted" bythe work piece-and i cvents the dogs from bending aroundthecenteri, f j V outer end; of the sleeve, inthis embodi f ment'fis machined down'to form a. circular knife oilge' l'9'whlch enters-the workpiece and helps At the innerend of the center pin 2| there is a spring adjusting screw 25 which'is tapped into the body of the center pin and held in position by look nut '26. 'Iheunthreaded end of'th'is aerew' has a spring engaging portion =21 that engages a compression spring 28) This spring worksinahole in shank ll of cup! andrests against a shoulder 29. This compression spring ms the conical center pi-n'i l outward until tho inner endofslot rests against screw point "andprevents"furtherr'mition.- 1 The spring 18 constitutes resilient means/for resisting thednward travel .oi the conical center mm: and thescrew 25 serves asm'eans foradresistanoe to "meet the requirements j ter' being us'ed; Thusyless endwi'se pressure of the cone maybe provided for thin walled work i which. is easy to split and greater pressure for harder or thicker walled work where the danger ol' splittingis less. .a v. i v "The outer end of the 'center'pin 21: is tapered in a double cone form, comprising an outermost portion 30 of relatively largelincluded angle and an adjacent; secondary work-engaging portion all of lesser included angle. 'The outermost cone section 30serves to shorten the overall length oi the biconical member and atrtheiz-sameetime permits work having a-prebored hole'to be picked up and guided onto the work "engaging cone surlace-3l.m M. A The purpose of the lesseri-n'cluded angle ofzthe work-engagingsurface-of the cone section 31 is to? provide "greater" pressure against the inner surface'of the-work piece; to causethe cone to enter the prebored hole more easilyland by virtue of greaterwedging action to exert greater pressure against the inner Ledges :of the work piece;

; Thus, it insures more perfect centering-Horne hole is not perfeotlyround or iftherefshould be i 25 splinters or burrs leftwithinvthe edge .oigthe hole from previous operationsp -A'lso, if the hole is slightly elliptical the wedgin g action or the .cone will force the fiat sides of the ellipse apart land will cause the sides lying on the longlaxisito en gage the cone rather than be thrust to one side which is often the case when acone of greater included ngleisused c When the :pressureiofthework piece against i the cone hasbecome suflicient to overcome the resistance of spring 28 the center: pin 2| slides inwardly. This permits the workpiece :to sen-gage successively circular knife edge manor sleeve li and then Wedge-Shaped ends 325of driving dogs l3. Finally, the end of the work piece such as shown at 33 in Figs lllcomes inicontact with the squared endface 20 of the sleeve 16. sThe circalar knifeeedg'e thisltaperedinwardly as shown at 34 to compress the material of the workpiece as it is forced. into, position and. thus provide a. ring of ldenser'material, between the, circular knifeand the conical center v-pingto be engaged by the drivingdogs l3. This arrangement makes it possible to transmit more powerxwithout tear ing the material. i y c Referring now more specifically to the driving dogs, I have shown in Figs. 3, 4 and 5am advan- I tageous form. In'the embodiment illustrated the shankor mainbody portion 350i the driving dog 13 issquar'ein cross-section as shown in Fig. 5B. In" operation thi'slsquare portion engages the dial;

side walls IBYthat define the keyways in thesleevc Hi? The threaded end I5 is roundedas. indicated inuFigs. 5A vand 5C. The work. engaging; endis wedge-shaped jiormingsa knife-like edge '32 as shown in Figs. 3 and 55D. As illustratedzin Fins. 3rand4, the-five driving does .areradially fill-1 ranged about the center axis. of the, disk They are spaced equal distances apart; 'andirom the center of the diskalthoug-h this isnot $65811. tial.

By virtue of the tapped connection between the disk l2 and the threaded, portion 15.5 :each of the driving dogs isindividually adjustable and ;replaceable. Sufiicient length is provided to. permit regrinding iofithe knife .edge 32 lfwthe. latter becomes worn, dull oris broken offs In such case the. repaired ;member Listhreaded less. dish tance; into the disk use as to .makeritz the, was effective lengthcasxthe other driving dogs. Also, the outward 5 extension .of knife. edged; portions .82

a above.

beyond. face of. sleeve, [6 may begadiusted? to the exact needs of the work being done. Thus,-

adjustments of joneor more. of the driving-dogs in either direction. maybe obtained. by turning the driver in the desired direetionflfand by virtue of this adjustability of the driving dogs their efiectivelifeyismaterially increased.

I-As :illustratedin j'Figs. c and 7, the sleeve l a, is; cylindrical in shape and has thetkeyways', for- It will be appreciated from the foregoing that a series of different diameter sleeves can be made to' fit; within the cup Hi and-havingexternal extended, diameters, such as: shown at 36 in Fig. l, of difi'erent dimensions. to fit various sizes of work. pieces-and internal diameters of varying sizes to receive conical center points having body portions of Varying diameters. In such cases the tapped holes in disk=l2 may be spaced asrequired to. provide proper alignment of the driving dogs IS with slots in the sleeves. Likewise, it will become apparent-'thatfor each inner sleeve diameter there may be a seriesof conical center points; each having the same body diameter to fit the sleeve, but having Work engaging cone surfaces in a series of diameters capableof fitting a .wide range of hole sizes.

Illustrative examples of these variations and alternatives are given in Figs:8-'-13, a more .detailed'description of which nowfollows. 1

Once the disk, is removed the arrangementi in which the cylindricalbody 11011-5:

tion orthe' center pin is changed-in acco dance: with the internal diameter of thesleeve, and by.

which theexternal extended portion .36-of sleeve lfimay be reduced to permit-theturning Ofsmall; :between the,

outside diameters without conflict cutting toolandthe sleeve. 1 In Figs. ;.12 .and 1-3 there is illustrated: an. al

ternative; form ot bodyportion andan alterna.-.; tive, form pf sleeve for the driving centers stead of having the sleeve housed within thebody; portion, the latter is madesolid and shortened.

. as d c d a and. the slee is ength ned:

driving'cen'ter end, .Thecenter pin 2i and the conesectionstll and;3l in. this embodiment are substantially the same as those shownin Fig.1, Another distinction between; this embodiment and those. shown-in preceding figures is that-no. disk or base member l 2 is used. Instead the driving dogs 13 are tapped directly intothe body member.

In Figs. 14' and 15 I have shown anfadaptationg of my driving center to afisolid (not'preboredi work piece. In this case a small ,diameter sta; tionary center pin-4T isused instead of the resil-y iently mounted center pin described above. This, center pin is threaded into a;-stationary"center;

' core48 and is adjustable-endwise byturning with I a screw driver inserted thescrewheadshown;

In'the driving center shown in Figs. .8 and!) the cup HI, sleeve l6,.and main body portion 2| of the center pin have been maintained sub-v stantially the same .in size and shape as the corresponding parts shown in the preceding figures.

' This is also true of the sleeve extension shown at 36.0 The change, however, comesin the biconical sections 31 and 38-01? the centerpin, whichhave been reduced in diameter toaccommodate the smaller bore in the prebored work piece 39. The sizes of the cone sections 31. and 38 bear a definite proper relationshipto the size and, bore of the work piece to insure properdrivingcontact and desired concentricity as explained .herein- In Figs. l0

[6 has been increased considerably in wall thickness. This produces a smaller diameter bore and thereby accommodates a smaller center pin. The exposed extension 36 of the sleevelhas been reduced proportionately in diameter to fit the smaller diameter center pin, and to permit the tool which forms the finished outside diameter of the work piece to produce work of smaller diameter while still clearing this extended portion36 of sleeve I6. The two cone sections 40 and 4| of this center pin are smaller in diameter than and 11 th'ecup l0 has been maintained the same diameter as beforeibut the sleeve at 49. By such adjustment thework engagingcenter point 50 may beadvanced toward or re,-

tracted from the solid work piece 5|. When the point center has been-adjusted to; the desired position it is locked-in place by the screw 52, which is threaded in the same hole, and abuts thecenter l'l."

The driving dogs 53 shown in Figs. 1c. and-17 are like the driving. dogs l3' o f Fig. 3 except that the shankor bodyportion 54fis circular in cross section, instead of rectangular- They are therefore adaptable for use in asleeve having either; rounded slots orflat sidedslots as mentioned hereinahove. Thesedriving dogs are tapped intov the disk member I 2 asin Fig.3, and to prevent. rotation about their axes, locking screws 52, such as shown in Fig. 14, are provided; Also, each of} the tapped ends hasa screw' head 49 for receive v ingya screw driver,-,-te!adjust the dogs endwise} by rotation in the proper. direction,-;; When the locking screws 52 are turned up to'give a tight 'cup, said extension having acircularknif edge formed at the forward end face. thereof, driving dogs. supported by said sleeve, :and. av center Slidg: ably mounted within .the sleeve forgengagingi the work. r ,1

driving members are maintained in nonrotative driving position by said sleeve.

3. A lathe driving center comprising a center work engaging pin, a cylindrical body, a concentric sleeve surrounded by said body and having an extended portion of reduced diameter, the outer end of said reduced diameter portion being formed into a circular knife edge.

4. A driving center comprising a supporting body portion adapted to be attached to a driving mechanism, said body portion having a bore, a sleeve in said bore and supportedly fixed internally to said body portion, said sleeve having internal longitudinal elongated slots opening the length thereof into the bore of the sleeve, elongated work-engaging driving members located and maintained non-rotatably withinthe slots of said sleeve, and a work-engaging center member located within the bore of said sleeve in contiguous longitudinally supporting relation to said driving members.

5. A driving center comprising, in combination, a'center member havin a conical, workengaging, outer-end portion, a concentric supporting sleeve in the bore of which said center member is located, an annular series of elongated longitudinal driving members in lengthwise contiguous relationship with said center member and located within radial, spaced, longitudinal 7 slots provided in the sleeve wall and opening into the bore of the sleeve, and a cup-shaped body member in which said sleeve and center member are held in concentric operative relationship.

6. A driving center comprising a cup-shaped body, a sleeve and a cooperating supporting base housed within said body, elongated driving members connected at their inner ends to said supporting base and having their intermediate portions located in annularly spaced, longitudinal slots provided in said sleeve coincident with its bore, said driving members having projected, Work-engaging, outer-end portions, and a workengaging center member mounted within the bore of said sleeve in supporting relation to the contiguous portions of said driving members in the slots of the sleeve.

7. A driving center comprising a supporting body adapted to be attached to rotating means, a sleeve detachably secured coaxially to and having a portion of reduced diameter extending beshaped, driving members located within and extending the length of said slots, and means within said supporting body and contiguous to the inner end of said sleeve for normally holding said so located driving members from longitudinal movement but permitting longitudinal adjustment of said driving members.

8. In a driving center having a supporting member adapted to be attached to a driving mechanism, a sleeve detachably secured coaxially to said supporting member, and a pointed center member located within the bore of said sleeve for centering a Work piece, the combination of a base slidably and removably positioned within said supporting member, and normally held in place by the innerend of said sleeve, and a plurality of elongated, polygonal, flat-sided driving members located in complementary slots in said sleeve, opening lengthwise into the bore of the sleeve, said driving members being attached to said base and longitudinally adjustable with respect to said base.

9. A driving center comprising a supporting body member, having a forwardly extending outer cup portion, a concentric inner sleeve fitted and removably secured within and extending beyond said cup portion and presenting a squared workengaging face of reduced diameter for accurate endwise positioning of the work piece, and a plurality of elongated, longitudinal driving members located within spaced longitudinal slots provided in the wall of said inner sleeve and opening lengthwise into the bore of the sleeve, said driving members having work-engaging ends projecting beyond said sleeve.

10. A driving center comprisin a body portion, a sleeve supported thereby, said sleeve having longitudinal elongated slots spaced around its inner circumference and opening the length thereof into the bore of the sleeve, elongated work-engaging driving members located substantially throughout their length within the elongated slots of said sleeve, means maintaining said driving members non-rotatably therein, and a work engaging center member concentrically located within the bore of said sleeve, and engaging said driving members for holding them in their yond said body, said sleeve having-a. plurality of I longitudinal, polygonal, flat-sided, slots formed within its body portion opening lengthwise into its bore, a plurality of elongated, complementary grooves.

11'. A driving center as defined in claim 10 and in which the work-engaging center member and EDGAR A. TER ELL. 

